The invention concerns an improved bag-on valve.
A bag-on valve is used in a distributor for a product under pressure such as for example an aerosol can.
A bag-on valve generally comprises a flexible bag made of impermeable material which is made for example of two synthetic layers placed on top of one another and welded together at their girth, whereby an opening is left which is closed by a valve making it possible to fill the bag with the desired product.
Such a bag-on valve is often rolled up or folded up, somewhat like a cigar, and it is maintained in the rolled-up position by a label glued round the rolled-up bag-on valve.
This rolled-up bag-on valve is then introduced in a recipient with an opening which is shut by the valve of the bag-on valve.
The distributor which is thus obtained by assembling the bag-on valve in the recipient is then filled with the product to be distributed on the one hand, which is introduced under pressure in the bag-on valve, and with a gas under pressure which fills the space formed between the recipient and the bag-on valve on the other hand and which serves as a pressure source for distributing the product when the valve is activated by means of a spray button mounted on the valve.
During the filling of the product, the label which maintains the bag-on valve in the rolled-up position is broken by the filling pressure of the product which makes the bag swell while unrolling or unfolding the bag.
The length of the rolled-up bag-on valve is chosen as a function of the height of the recipient, such that the length is equal to the height of the recipient, as a result of which it can contain a maximum quantity of the product.
Only, while filling it with the product, the length of the bag-on valve becomes shorter as the bag is being filled, since the bag swells and expands laterally, which is disadvantageous in that the filled bag does not rest on the bottom of the recipient and, as a result, the bag containing the weight of the product is completely suspended on the valve, which implies that the bag will easily tear if the distributor is dropped by accident.
When the bag is unrolled while being filled with the product, there will be another problem in that the bag often has two upper corners which extend laterally and which hinder the unrolling movement as these corners come into contact with the inner wall of the recipient, resulting in the bag being twisted round the valve.
On the one hand, this twisting of the bag makes the bag weak, such that the bag may tear due to the effect of the mere twist, or due to the fact that, because of the twist, the filling volume is not sufficient to contain the quantity of product that is injected in case of an automatic filling.
On the other hand, the weakening caused by the twist makes the bag tear quicker when the distributor falls on the ground.
A disadvantage connected to the use of the label for maintaining the bag-on valve in the rolled-up position is that this label hinders the unfolding of the bag, thus causing a twist during the filling phase, which results in a weakening as described above.